ISN Audio CU4 Cable Review







ISN Audio CU4 Upgrade Cable Review


ISN Audio is a relative new Chinese brand that is producing portable audio gears like Earbuds, In-Ear Monitors and Cables.

The ISN Audio CU4 is a 4 core High Purity Single Crystal Copper upgrade cable with 115 strands and 460 wire (4×115) conductors in total.



I would like to thank ISN Audio for providing me the CU4 Upgrade Cable sample via Penon Audio for review purposes. I am not affiliated with ISN Audio and Penon Audio beyond this review and these words reflect my true and unaltered opinions about the product.



The Price:

The ISN Audio CU4 upgrade is available for 149,00 USD with MMCX and 2-Pin connectors. You have also the option to choose one of the 3.5mm unbalanced, 2.5mm balanced and 4.4mm Balanced (+10,00 USD) headphone plug.



Package and Accessories:

The ISN Audio CU4 upgrade cable came in a pretty small rectangular cardboard box that features some product brandings on the top.

The box is containing the following items:

  • 1 pcs x ISN Audio CU4 upgrade cable
  • 1 pcs x Zipper Case
  • 1 pcs x Cleaning Tool
  • 1 pcs x Carabineer



Technical Specifications:
  • Material : High Purity Single Crystal Copper Wire Material
  • Cores : 4 Cores
  • Strands : 115 Strands
  • Conductors : 460 Conductor Wires (4×115)
  • Interface : MMCX or 2PIN 0.78mm
  • Plug Options : 3.5mm Unbalanced, 2.5mm Balanced and 4.4mm Balanced (Rhodium Plated)
  • Cable Length : 1.2m




Design and Build Quality:

The ISN Audio CU4 is one of the higher level upgrade cables of the company that is made of Single Crystal Copper wire material. The cable has 4 cores and each core has 115 strands which makes 460 conductor wires in total. The total length of the cable is about 1.2 meter and looks very good in terms of craftsmanship.

The cable has a soft transparent PVC plastic insulation with a very low amount of microphonic effect.

The MMCX connectors have a metal housing in black color with L & R markings and two rings on each connector in gold color which gives the CU4 a nice stylish look.

The CU4 is available in two connector options, which are the MMCX (Micro Miniature Coaxial) and the 2-Pin (0.78mm) variant with male connectors. The joints are made of silver containing tin material.

Both connectors do features transparent plastic strain relieves to protect the connectors from damages.

The Y-splitter sports the ISN Brand logo and two gold rings/circles while the chin slider shows the CU4 branding and has one gold ring.


The ISN Audio CU4 features a Rhodium plated headphone plug that has a straight profiled headphone jack and is available in 3.5mm TRS unbalanced and 2.5mm TTRS or 4.4mm TRRRS (Pentaconn) balanced variants.

The headphone housing has a very stylish look and is made of metal in black color and features the same gold colored rings that we have seen on the other metal part of the CU4.

The ISN Audio CU4 is one of the best looking and very well made Upgrade Cables I have used to date.



Equipments used for this review:
  • Cables            : ISN Audio CU4 Upgrade Cable
  • IEM’s              : ISN Audio H40, Campfire Audio ARA & ATLAS, Final Audio E4000
  • Sources         : FiiO M11 Pro, iBasso DX220 MAX



Albums & tracks used for this review:
  • Sting – Englishman in New York – (Flac 24bit/48kHz)
  • Eric Clapton – Wonderful Tonight (Flac 24bit/96kHz)
  • Dave Gahan – Kingdom (Tidal Hi-Fi)
  • B.B. King – Riding With The King (Flac 24bit/96kHz)
  • Chopin – Nocturn No. 20 In C-Sharp Minor (Flac 16bit/44.1kHz)
  • Edith Piaf – Non Je Ne Regrette Rien (Flac 24bit/48kHz)
  • Diana Krall – So Wonderful (DSF)
  • First Aid Kit – My Silver Lining (Flac 16bit/44.1kHz)
  • Sertap Erener – Aşk (Flac 16bit/44.1kHz)
  • London Grammar – Interlud (Live) (Flac 24bit/44kHz)
  • Laura Pergolizzi – Lost On You “Live at Harvard and Stone” (Tidal Hi-Fi)
  • Fazıl Say – Nazım Oratoryosu (Live) (Flac 16bit/44.1kHz)
  • Vivaldi – Le QuarttroStagioni “The Four Season” (Tidal Hi-Fi)
  • Otto Liebert& Luna Negra – The River (Spotify)
  • Armin Van Buuren – Vini Vici (Flac 16bit/44.1kHz)
  • No Doubt – Hella Gut (Flac 16bit/44.1kHz)
  • Lorde – Royal (Flac 24bit/48kHz)
  • Massive Attack – Angel (Flac 24bit/192kHz)
  • Twerl – Lishu (Spotify)
  • U2 – Sunday Bloody Sunday (Flac 16bit/44.1kHz)
  • Portishead – The Hidden Camera (MP3 320kpbs)
  • Metallica – Sad but True (Flac 24bit/96kHz)
  • Opeth – Windowpane (Flac 16bit/44.1kHz)
  • Megadeth – Sweating Bullets (Tidal Hi-Fi)
  • Rush’s – Leave That Thing Alone (Flac 16bit/44.1kHz)
  • Slayer – Angel of Death (Spotify)
  • Tom Player – Resonace Theory “Album” (Tidal Hi-Fi)
  • Liquid Tension Experiment 2 – Acid Rain (Spotify)






The Sound:

I have tested the ISN Audio CU4 upgrade cable with my ISN Audio H40, Campfire Audio ARA, Campfire Audio ATLAS and Final Audio E4000 In-Ear Monitors to hear the changes and improvements compared to their stock cables.

Bass / Midrange / Treble / Soundstage:

The ISN Audio CU4 is made of Single Crystal Copper material which means that the most audible difference will be occur in the lower frequency region like with most pure cooper cables.

When I connected the CU4 to the Final Audio E4000 and Campfire Audio ARA I have immediately noticed that the subbass region has shown a better level of depth, intensity and extension compared to their stock cable.

The ISN Audio CU4 gives also the midbass region additional body and fullness without to make the overall presentation muddy or veiled, which is a big plus point of the CU4. The CU4 added the ISN Audio H40 additional texture and control compared to its stock cable, which was otherwise pretty good.

Instruments like snare drums and guitars have gained more weight and fullness especially paired with the Final Audio E4000 and Campfire Audio ARA. The difference in terms of when paired with the Campfire Audio ATLAS was less audible.

The ISN Audio CU4 shows a pretty audible difference in the lower midrange region and gives the overall presentation in the midrange region slightly more body and musicality. The Final Audio E4000 and ISN Audio H40 gained more body while listen to instruments like electric guitars, pianos and hi-hats. Also soprano voices do sound more musical, have more depth and are more emotional especially with the Campfire Audio ARA compared to its stock cable.

The upper midrange smoothed out and the transition are more controlled with all IEM’s I have tested with the ISN Audio CU4. The treble extension and brightness remained pretty unchanged while some minor but pretty noticeable changes happened to treble intensive instruments like cymbals, kick drums or soprano voices that have been smoothed out in a noticeable manner, especially with the Final Audio E4000 and ISN Audio H40.

The treble notes do sound slightly thicker and while the rendered air remains almost the same.

The soundstage of all IEM’s I have tested with the ISN Audio CU4 showed minor differences with focal point to the wideness, while the most audible difference was with the Campfire Audio ARA.




The ISN Audio CU4 is beautiful looking and very well made upgrade cable that offers pretty audible sound improvements especially in terms of subbass depth and midbass control & intensity. It adds also a nice amount of fullness and musicality to the midrange without to affect the overall clarity, while the treble region will be smoothed out without to scale down the overall sparkle and airiness of this area.



Pros and Cons:
  • + Very audible improvements in terms of bass depth, intensity & extension
  • + Adds fullness/body to the midrange without to downscale the overall clarity and airiness
  • + Beautiful Look & Very Good Build Quality
  • + Available with a wide variety of plugs and connectors


  • – Looking forward for a more appealing packaging






You may also like...

2 Responses

  1. Nap James Labajo says:

    Can you can compare this to Fiio LC-RE mmcx. I’m currently using FH-7 and planning to upgrade my cable since I’ve read that FH-7 are cable sensitive.

    • Gökhan AYDIN says:

      Hi there, Sorry but I didn’t have had the chance to pair the FH7 with the LC-RE cable. But the ISN Audio CU4 pairs quite well with the FH7. Cheers!

Leave a Reply

Your email address will not be published. Required fields are marked *